As a user interface, a display device may be mounted on an electronic device, and in order to provide for a light weight, thin, short, and small electronic device having low power consumption, a flat display device is widely used as the display device.
Since a liquid crystal display (LCD), that is, the currently most popular flat display device, is a light receiving device that displays an image by adjusting the amount of light received from the outside, a backlight unit (BLU) including an additional light source for emitting light to a liquid crystal panel, that is, a backlight lamp, may be used. Recently, a light emitting diode (LED) having characteristics of low power consumption, eco-friendly, and slim design is extensively used as a light source.
Amorphous Silicon (a-Si) used for a thin film transistor (TFT) LCD is sensitive to light. That is, when irradiated with light, an a-Si thin film has a conductor property, and thus, its resistance is reduced, and when the light is removed, the a-Si thin film has a non-conductor property, and thus, its resistance becomes relatively larger, so that the a-Si thin film is affected by a charging voltage of a liquid crystal capacitor. Additionally, in some cases, when irradiated with light, the a-Si thin film causes an increase of parasitic capacitance, so that a screen noise phenomenon may be seen.
When the light of a backlight unit is emitted uniformly, since this affects the front surface of a liquid crystal panel evenly, there may be no problems. Suggested is a Pulse-Width Modulation (PWM) luminance adjustment method for turning on/off a backlight unit periodically in order to improve the image quality aspects.
In the PWM luminance adjustment method, if a ratio of a sync signal frequency and a PWM frequency is not identical or substantially identical, the movement of a regular band may be observed in each frame. This phenomenon is called waterfall noise.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form prior art.